Wood sheet and method for manufacturing the same

ABSTRACT

Disclose are a wood sheet and a method for manufacturing the wood sheet. In particular, the real wood sheet is prepared with natural wood sheets used for interior and exterior materials, a binder and a stiffener, thereby providing patterned veneer appearance. Further, the wood sheet may have improved physical properties and reduced weight and be manufactured with reduced cost.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a Divisional of Application of U.S. patentapplication Ser. No. 14/562,692 filed on Dec. 6, 2014, which claimsunder 35 U.S.C. § 119(a) the benefit of priority to Korean PatentApplication No. 10-2013-0157329 filed on Dec. 17, 2013, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a wood sheet and a method formanufacturing the real wood sheet. The wood sheet may be prepared with apatterned wood sheet which is used for interior and exterior materials,a binder and a stiffener, thereby proving the patterned veneerappearance. The wood sheet of the present invention may have improvedphysical properties and reduced weight and may be manufactured withreduced cost.

BACKGROUND

Materials having a patterned veneer texture have been widely used toexhibit external natural beauty and high-quality elegant effects asvarious interior and exterior materials.

Real wood materials having a patterned veneer texture are used ininterior and exterior materials, various structures, vehicle interiormaterials, and electric and electronic products and the like, and aretypically prepared and used in a sheet form for manufacturing processand natural appearance.

The wood sheet generally having a multilayer structure includes apatterned veneer attached to an external-most layer of a stiffener inwhich an aluminum sheet is inserted between veneers, as shown in FIG. 1,and thus suitable form of sheets may be manufactured. In other words, asshown in FIG. 1, a conventional real wood sheet is formed with 7 layersthat include: a patterned veneer (1), an adhesive layer (20) a technicalveneer (3), an adhesive layer (4), an aluminum sheet (5), an adhesivelayer (6) and a veneer layer as an internal layer adjacent to an ejectedsubstrate (7), and is applied to the ejected substrate (8). Since threeadhesive layers and an aluminum sheet are inserted between veneers,manufacturing costs may increase due to the complicated manufacturingprocess.

Meanwhile, in the related art, a wood sheet in an automotive interiormaterial obtained by injection molding a resin has been developed. Thewood sheet is formed with a patterned veneer layer formed on the ejectedresin surface, and a strength stiffener such as non-woven fabricattached to the bottom of the patterned veneer as an adhesive, and anelastic layer formed by spraying or coating a material selected frompolyurethane, rubber or silicone that provides softness to the patternedveneer at the bottom, and an ejected resin substrate. The wood sheet maybe used for vehicle interior materials such as dash board exteriorpanels, instrument exterior panels, audio deck exterior panels, missionbox exterior panels and door trim exterior panels.

Although the above real wood sheet has a fairly advanced structurecompared to conventional wood sheets, however, it has a complicatedstructure with a patterned veneer, an adhesive, a stiffener, an elasticlayer and the like, and thus, many defects may occur during theprocesses in which the adhesive and the elastic layer are used.

In addition, in other related example, a molding method of a resin moldcomponent having a wooden board as a surface material has been reported.The wooden board includes a protective board attached to the reverseside of a patterned veneer or wooden decorative board as an adhesive.

However, the above structure also has a problem. For example, thepatterned veneer and the protective board are readily delaminated due toheterogeneity between them, and consequently, durability is inferior,and weight thereof may not be reduced sufficiently.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

In a preferred aspect, the present invention provides a wood sheet whichmay have substantially improved physical properties and reduced weightand be manufactured with reduced cost. The wood sheet may be preparedwith a conventional natural wood sheet such as a patterned veneer, abinder and a stiffener.

Accordingly, the wood sheet may be formed with a simple structure of apatterned veneer, a binder and a stiffener, and may have substantiallyimproved moldability and physical properties while having reducedweight.

In a further preferred aspect, provided is a method for manufacturing awood sheet prepared with a simple structure of a patterned veneer, abinder and a stiffener.

In an exemplary embodiment, the wood sheet may include a patternedveneer, an adhesive soft binder, and a stiffener. In particular, thebinder may have a melting temperature of about 80 to 200° C. and thestiffener may be formed with non-woven fabric of 30 to 200 g/m².

In an exemplary embodiment, the method for manufacturing a real woodsheet may include: preparing a patterned veneer, an adhesive soft binderand a stiffener; cutting the prepared patterned veneer and abinder-attached stiffener prepared from the adhesive soft binder and thestiffener into primary shapes; providing the primary shaped patternedveneer and the binder-attached stiffener in a mold having a targetshape; and press molding the mold provided with the patterned veneer andthe binder-attached stiffener to form a wood sheet through pressing. Inparticular, the binder may have a melting temperature of about 80 to200° C. and the stiffener may be formed with non-woven fabric of 30 to200 g/m².

Further provided are injection molded products including the wood sheetas described herein. Still further provided are vehicles includingautomotive vehicles, that use or comprise the wood sheet of theinvention as an interior or exterior material.

The wood sheet according to the present invention may include naturalwood having simplified structure and reduced weight, and may bemanufactured to have substantially improved physical properties withoutusing an aluminum sheet. Accordingly, high-quality interior materialsfor various interior products may be provided.

In addition, according to the present invention, a high-quality woodsheet may be manufactured with reduced cost and simple process, and thusmay be used as interior components for various structures at low costs.

Particularly, luxurious appearance of products may be provided andproduct values may be increased economically when the wood sheet of thepresent invention is used for vehicle interior components or homeappliances.

Other aspects and preferred embodiments of the invention are discussedinfra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present invention, and wherein:

FIG. 1 illustrates a cross-sectional view of a wood sheet using aconventional aluminum sheet in the related arts;

FIG. 2 illustrates a cross-sectional view of an exemplary wood sheetaccording to an exemplary embodiment of the present invention; and

FIG. 3 illustrates an exemplary process of manufacturing an exemplarywood sheet according to an exemplary embodiment of the present.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the present invention asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

Unless specifically stated or obvious from context, as used herein, theterm “about” is understood as within a range of normal tolerance in theart, for example within 2 standard deviations of the mean. “About” canbe understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%,0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear fromthe context, all numerical values provided herein are modified by theterm “about”.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g. fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

Hereinafter reference will now be made in detail to various exemplaryembodiments of the present invention, examples of which are illustratedin the accompanying drawings and described below. While the inventionwill be described in conjunction with exemplary embodiments, it will beunderstood that present description is not intended to limit theinvention to those exemplary embodiments. On the contrary, the inventionis intended to cover not only the exemplary embodiments, but alsovarious alternatives, modifications, equivalents and other embodiments,which may be included within the spirit and scope of the invention asdefined by the appended claims.

The present invention relates to, as shown in FIG. 2, a wood sheet maybe formed with a patterned veneer (11), an adhesive soft binder (12) anda stiffener formed with non-woven fabric (13), and thus, the wood sheetmay have a simplified structure. In particular, the stiffener (13) maydirectly contact with an ejected substrate (14).

According to the present invention, the patterned veneer may be locatedat the top layer of the wood sheet in a sliced shape, and thus providean improved wood texture to the exterior and the surface. The patternedveneer may be formed in a thin plate veneer that is prepared by slicinga patterned natural wood or veneer and the like. Accordingly, thepatterned veneer sheet having a desired exterior pattern may be used ina single sheet. The patterned veneer may have a thickness of about 0.2to 1 mm, or particularly of about 0.4 to 0.8 mm.

The adhesive soft binder used in the present invention may have amelting temperature of about 80 to 200° C. The binder may have adhesivestrength and further have a function to block ejection pressure duringlaminating with a stiffener. In addition, the binder may providesoftness to the wood sheet, in contrast that conventional interlayeradhesives in a conventional wood sheet have only adhesive function. Inaddition, the binder may reduce the weight of the wood sheet as asubstitute for a technical veneer and an aluminum sheet. As such, weightof the wood sheet may be reduced and manufacturing cost thereof may bereduced.

As described above, the binder of the present invention may provideadhesive strength and softness between a patterned veneer and astiffener. The binder may be an organic adhesive, but not limited to,selected from urethane-based resin, acrylic-based resin, ester-basedresin and amide-based resin. In particular, the binder may be selectedfrom the group consisting of urethane-based hot melt (H/M),thermoplastic polyurethane (TPU) and ethylene vinyl acetate (EVA).Further, thermoplastic polyurethane resin may be used as the binder. Dueto optimal use of the binder, improved adhesive strength may be providedbetween the patterned veneer and the stiffener, aggregation inside thebinder may be improved surface tacky property may be adjusted.

The binder may have a melting temperature of about 80 to 200° C. Whenthe melting temperature is less than a predetermined temperature or lessthan about 80° C., adhesive strength may be reduced and layerdelamination may occur in the wood sheet, thereby deteriorating variousproperties. When the melting temperature is greater than about apredetermined temperature of greater than about 200° C., the processingtemperature needs to be increased substantially for obtaining anadhesive property during the process for manufacturing the wood sheet.In such substantially elevated temperature, the patterned veneer may becarbonized, or a binder may leak to the surface through pores in thepatterned veneer, thereby generating undesirable gloss on the surface ofthe patterned veneer. Particularly, when the binder is used as aninterior material, for example, interior components for a vehicleexposed under sunlight or hot weather condition, light resistance may berequired. Accordingly, the binder with non-yellowing property and havinga melting temperature of 120 to 200° C. may be particularly used forheat resistance and light resistance.

The binder may be applied by generally used methods in the arts, such asmelting or spraying, or may be applied as liquid or solid binder.Particularly, the binder may be prepared and processed in a sheet orfilm form, or the binder may be laminated in advance by layering on astiffener during press molding process for manufacturing the wood sheet.When a liquid or solid binder is used, layer delamination may occur dueto nonuniform adhesion, or mold attachment may occur due to substantialadhesion thereby causing defects.

The stiffener, as used herein, may be adjacent to the binder and thestiffener may be formed with a non-woven fabric of about 30 to 200 g/m²,or particularly of about 70 to 120 g/m².

The stiffener may adhere to an ejected material, and may serve as a backsheet of the wood sheet as adhering to the binder. As such, thestiffener may provide rigidity to the real wood sheet.

The stiffener may be a non-woven fabric having strength capable ofreplacing an aluminum sheet and enduring ejection pressure as beinglaminated with the binder after molding. Further, the stiffener mayprovide improved moldability. Accordingly, the non-woven fabric withouttextures may be used instead of knit having a directional property. Inaddition, in the wood sheet molding process, when a product is removedfrom the mold after an injection molding and a PUR (Polyurethane RIM)process, adhesive force at the interfaces may be advantageous. When theadhesive power is less than a predetermined value, delamination mayoccur at the interfaces in the wood sheet product. In addition, whenshort fiber non-woven fabric is used, delamination at the interfacesbetween non-woven fabric may occur, and accordingly, long fibernon-woven fabric having high tensile strength prepared by a span bond ora needle punching may be used. Particularly, the non-woven fabric spunmay be a mixture of polyethylene terephthalate (PET) and nylon. Theweight ratio of PET and nylon in the non-woven fabric spun may be in aratio between about 8:2 and 7:4. For example, filaments of the twocomponents of PET and nylon may be spun as microfilaments and separatedinto several threads. When non-woven fabric is used as a back sheet andor a stiffener to maintain rigidity, molding and physical propertiessuch as elongation may be improved.

Moreover, when the wood sheet described above is used for injectionmolding product, the stiffener may use non-woven fabric having a densityof about 30 to 200 g/m² to provide desired adhesive property with theinjection molding product material and to improve the rigidity as a backsheet capable of enduring ejection pressure. As such, the wood sheet maybe formed with substantial physical properties or binder may not beexposed to the surface. The non-woven fabric may have a thickness ofabout 0.4 to 2.0 mm, or particularly of about 0.4 to 1.0 mm. Inaddition, the non-woven fabric may be a long fiber non-woven fabric.

The wood sheet according to the present invention having a structure asdescribed above may include natural wood pattern and have simplifiedstructure and reduced weight. The wood sheet may also be prepared tohave improved physical properties without using an aluminum sheet, andthus, may be economically used as a high-quality plaster in interiorproducts with various wood textures.

Meanwhile, the real wood sheet according to the present invention suchas above may be manufactured by cutting raw materials such as apatterned veneer, an adhesive soft binder and a stiffener into primaryshapes, providing the cut materials in a mold having a target shape, andthen press molding the cut materials.

In FIG. 3, exemplary processes for manufacturing the wood sheetaccording to an exemplary embodiment of the present invention areillustrated. The method for manufacturing a wood sheet typicallyinclude: preparing raw materials such as a patterned veneer, a binderand a stiffener; cutting the raw materials into primary shapes; provingthe cut materials in a mold; press molding such as wood pressing,completing pressing and the like. An operation of providing the cutmaterial in the mold may include: preparing mold, preparing press andinstalling sheet inside the press mold.

The patterned veneer may be prepared as a single sheet as describedabove and the binder may be prepared with the adhesive soft binderhaving a melting temperature of about 80 to 200° C. in a sheet or filmform. The stiffener may be either prepared with a stiffener made ofnon-woven fabric in a separate sheet form or prepared in the form of astiffener formed with non-woven fabric having density of about 30 to 200g/m² being laminated with the adhesive soft binder. Particularly, asdescribed above, the binder may be coated on the stiffener using commonmethods and prepared in a laminated form, or the binder may be preparedin a sheet or film form, and then the formed binder may besimultaneously laminated with the stiffener and a wood press.Alternatively, the patterned veneer, the binder in a sheet or film form,and the stiffener may be independently prepared in each sheet form. Whenthe binder is prepared in a sheet or film form, the thickness may be ofabout 0.3 to 1.5 mm, or particularly of about 0.4 to 0.8 mm forlamination or typical pressing conditions.

The prepared patterned veneer, the binder and the stiffener may belaminated in sequential order, and may be cut into the primary shapes.As used herein, the “primary shape cutting” means that the a primaryshape may be determined temporarily into a rough to form in a sufficientsize for obtaining the final shape of the wood sheet. As such, forsubsequent pressing, materials may be cut into the primary shapesufficient for press molding. An operation of cutting may be performedby adjusting the patterned veneer, the binder, the stiffener and thelike into the primary shapes particularly using laser.

The cut materials, i.e. patterned veneer, binder and stiffener, may beprovided to a mold having a target shape. The mold may be prepared tohave a shape matching to a component to be manufactured, and the processherein may include: preheating the mold to a temperature of about 130 to160° C. in advance for press molding and removal of mold thereafter,setting the pressure to about 25 to 35 bar, and preparing the mold bywaxing the mold surface. In addition, the mold may be prepared in apress capable of adjusting temperatures, pressures and times for pressmolding.

The real wood sheet may be manufactured after pressing the primaryshaped sheets set in the mold, and then molding the sheets into the woodsheet. In particular, the mold may be opened at about 2 to 5 mm afterfirst pressing and then second pressing may be carried out to remove thegas generated in the sheet during the press molding process and toprevent molding defects.

The wood sheet according to the present invention manufactured asdescribed above may be further injection molded by ejecting the moldedcomponent. The injection molding may be carried out on the stiffenersurface of the wood sheet and a molding product may be obtained byinjection molding with the wood sheet.

As such, an injection molded product including the wood sheet accordingto the present invention may be provided.

The injection molding products may include vehicle interior componentsor vehicle interior products such as dash board exterior panels,instrument exterior panels, mission box exterior panels, door trimexterior panels, audio deck exterior panels and the like.

As described above, according to various exemplary embodiment of thepresent invention, the high-quality wood sheet may be obtained withsimplified structure than conventional wood sheets, and further may havea combined structure by injection molding, such that the productobtained with the wood sheet may have unique properties in an economicaland simple manufacturing. Consequently, the wood sheet and the method ofmanufacturing thereof may be applied to other interior components ofvarious structures at reduced costs.

Particularly, the wood sheet according to the present invention may haveimproved durability and substantially improved quality textures whenused for vehicle interior components, home appliances, indoor interiormaterials or the like, and thus, product values may be improved byhigh-quality and reduced-weight thereof at reduced cost.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to an example, however, the present invention is not limitedto the example.

Example

A natural patterned veneer having length, width and thickness of about0.5 mm for the size of a component to be molded was prepared. Anadhesive soft binder made of a polyurethane resin having melting pointof about 120° C. and a thickness of about 0.5 mm and the same sizedpatterned veneer was prepared. In addition, as a stiffener, non-wovenfabric having thickness of about 0.5 mm and density of about 100 g/m²formed with PET and nylon-6 in a weight ratio of about 7:3 was preparedto have the same size as described above.

The binder was prepared by being laminated to the stiffener in advanceusing a T-die method.

The patterned veneer and the binder-laminated stiffener prepared asdescribed above were cut into primary shapes for a vehicle interiorcomponent such as door trim exterior panel using laser, and the cutmaterial was provided to a press mold in which the temperature wasadjusted to about 140° C., the pressure to about 30 bar for about 180sec for laminating. Thus the sheet was fixed. Herein, the mold waspreheated to about 150° C. and the surface thereof was treated bywaxing.

The primary shaped sheets provided to the mold were fixed at the cornerholes of the press mold under the condition as described above, and waspressed. The molding was completed by opening by about 3 mm after firstpressing, and then carrying out second pressing, and thus, a wood sheetfor a door trim exterior panel was manufactured which may be used for avehicle interior component.

Comparative Examples 1 to 5

Comparative examples were carried out as described in Example, butconditions listed in Table 1 were applied for each comparative example.

TABLE 1 Example Comparative Example Category 1 1 2 3 4 5 PatternedVeneer Thickness (mm) 0.5 0.1 0.4 0.5 0.5 Product having a structure ofFIG. 1 Binder Thickness (mm) 0.4 0.4 0.2 0.4 0.4 Melting Point (° C.)120 120 120 70 120 Stiffener Weight (g/m²) 100 100 100 100 20

Test Example

Physical properties were measured comparing to the physical propertiesof the wood sheets of Example and Comparative Examples havingconstitutions of Table 1 and FIG. 1 and the results are shown in thefollowing Table 2.

Herein, the physical properties were measured using the methods shownbelow.

[Physical Property Measurement Method]

1) Moisture Resistance

Test pieces were left unattended for about 168 hours in a chamber undera condition of a test temperature of about 50±2° C. and relativehumidity of about 95±2% RH, and then were taken out for exteriorevaluation such as discoloration, fading, swelling, surface cracks, lossof gloss and interlayer cracks and the like were identified.

2) Heat Resistance

Test pieces were left unattended for snouy 300 hours in a chamber undera condition of a test temperature of about 80±2° C., and then were takenout for surface exterior evaluation such as discoloration, fading,swelling, surface cracks, loss of gloss and interlayer cracks and thelike were identified.

3) Light Resistance

After test pieces were irradiated under XENON ARC until totalaccumulated quantity of light reached about 700 KJ/m² under a conditionof a black panel temperature of about 89±3° C., inside humidity of about50±5% RH and irradiation intensity of about 0.55±0.02 W/m² (at awavelength of about 340 nm), the test pieces were taken out, and thepainted test pieces were washed with an aqueous neutral detergentsolution and dried with air for exterior evaluation such asdiscoloration, fading, swelling, surface cracks, loss of gloss andinterlayer cracks and the like were identified.

4) Thermal Cycling Resistance Property

A cycle of [80±2° C.×3 h→room temperature 1 h→−40° C.×3 h→roomtemperature 1 h→50±2° C., 95% RH or higher×7 h→room temperature 111] wasrepeated 3 times, and then the test pieces were taken out for surfaceexterior evaluation such as discoloration, fading, swelling, surfacecracks, loss of gloss and interlayer cracks and the like wereidentified.

TABLE 2 Example Comparative Example Category 1 1 2 3 4 5 moistureresistance ⊚ Δ Δ X X Δ heat resistance ⊚ ◯ ◯ X Δ ◯ Light Resistance ⊚ Δ◯ Δ ◯ ⊚ Thermal Cycling ⊚ ◯ Δ X Δ ◯ Resistance Property ⊚: VeryExcellent ◯: Excellent Δ: Fair X: Poor

As shown in Table 2, the product of the present invention was identifiedto have substantially improved physical properties except when thepatterned veneer had a thickness less than the range as described above(Comparative Example 1) or when the binder was treated less than therange as described above (Comparative Example 2). Accordingly, theproduct of Example according to the present invention was identified tohave substantially improved physical properties with simplifiedstructure reduced weight compared to the conventional product ofComparative Example 5. Further, in Comparative Examples 1 and 2, theproducts were manufactured to have a structure of the present invention,but physical properties thereof were similar to the conventional productof Comparative Example 5.

However, in applying the present invention, when the melting point ofthe binder was less than or out of the range as described (ComparativeExample 3), or when the density of the non-woven fabric was less thanthe density range as described above (Comparative Example 4), productsqualities were inferior so real products were not obtained.

According to the present invention, a high-quality wood sheet havingsimplified structure from the conventional wood sheets may be obtained,and may also be manufactured as a reduced weight product in aneconomical and simple process, as such, the wood sheet and the method ofmanufacturing thereof may be applied to interior components of variousstructures at low costs.

Particularly, the wood sheet according to various embodiments of thepresent invention may be used for vehicle interior components, homeappliances, interior decorating products or the like as a high-qualityinterior material with wood textures.

The invention has been described in detail with reference to exemplaryembodiments thereof. However, it will be appreciated by those skilled inthe art that changes may be made in these embodiments without departingfrom the principles and spirit of the invention, the scope of which isdefined in the appended claims and their equivalents.

What is claimed is:
 1. A method for manufacturing a wood sheet, consisting of: preparing a patterned veneer, an adhesive soft binder having a melting temperature of about 80 to 200° C., and a stiffener formed with a non-woven fabric having a density of about 30 to 200 g/m²; cutting the prepared patterned veneer and a binder-attached stiffener prepared from the adhesive soft binder and the stiffener into primary shapes; providing the primary shaped patterned veneer and the binder-attached stiffener in a mold having a target shape; and press molding the mold provided with the patterned veneer and the binder-attached stiffener to form a wood sheet through pressing, wherein the patterned veneer's thickness is 0.2 to 0.5 mm, wherein the adhesive soft binder's thickness is 0.3 to 0.4 mm, wherein the stiffener's thickness is 0.4 to 2.0 mm, wherein the stiffner is a non-woven fabric which is a mixture of polyethylene terephthalate(PET) and nylon-6, and wherein the weight ratio of PET and nylon-6 is between 8:2 and 7:3.
 2. The method of claim 1, wherein the binder is used in a sheet or film form.
 3. The method of claim 1, wherein the binder is laminated with the stiffener before cutting.
 4. The method of claim 1, wherein the press molding is carried out by the mold being opened by about 2 to 5 mm after first pressing and then second pressing is carried out. 